Parameterized constructor in Java - Mini Project: Build & Apply

Parameterized constructor

📖 Scenario: You are creating a simple Java program to represent a Book in a library system. Each Book has a title and an author.

🎯 Goal: Build a Java class Book with a parameterized constructor to set the title and author when creating a new Book object.

📋 What You'll Learn

Create a class called Book with two String fields: title and author.

Add a parameterized constructor to Book that takes two parameters: title and author.

Create a main method in a class called Library.

In main, create a Book object using the parameterized constructor with the title "The Alchemist" and author "Paulo Coelho".

Print the book's title and author using System.out.println.

💡 Why This Matters

🌍 Real World

Parameterized constructors are used in real-world programs to create objects with specific starting values, like setting up a book's title and author when adding it to a library system.

💼 Career

Understanding constructors is essential for Java programming jobs, as it helps in creating flexible and reusable code for object initialization.

1

Create the Book class with fields

Create a class called Book with two String fields named title and author.

Java

public class Book {
    // Your code here
}

Need a hint?

Think of title and author as labels on a book to store its name and writer.

2

Add a parameterized constructor

Add a parameterized constructor to the Book class that takes two parameters: String title and String author, and assigns them to the class fields.

Java

public class Book {
    String title;
    String author;

    // Add constructor here
}

Need a hint?

The constructor sets the book's title and author when you create a new Book object.

3

Create the Library class with main method

Create a class called Library with a main method. Inside main, create a Book object named myBook using the parameterized constructor with title "The Alchemist" and author "Paulo Coelho".

Java

public class Book {
    String title;
    String author;

    public Book(String title, String author) {
        this.title = title;
        this.author = author;
    }
}

public class Library {
    public static void main(String[] args) {
        // Create Book object here
    }
}

Need a hint?

The main method is the starting point of the program where you create your book.

4

Print the book's title and author

In the main method of Library, add two System.out.println statements to print the title and author of myBook.

Java

public class Book {
    String title;
    String author;

    public Book(String title, String author) {
        this.title = title;
        this.author = author;
    }
}

public class Library {
    public static void main(String[] args) {
        Book myBook = new Book("The Alchemist", "Paulo Coelho");
        // Print title and author here
    }
}

Need a hint?

Use System.out.println(myBook.title); and System.out.println(myBook.author); to show the book details.